Pesticide Residue Recoveries from Surface Wipes

Abstract:

Human exposure is a consequence of pesticide use indoors with a primary source resulting from residue deposition on household surfaces. Accurate measurements of surface residues is essential for estimating exposure from different routes. Various procedures have been developed for measuring pesticides including surface wipes with solvent moistened gauze pads, which is commonly used by the USEPA. However, surface wiping procedures differ in sampling material (e.g., gauze brand), solvent type, solvent volume, and number of wipes collected per sample. A standardized surface wipe sampling procedure is needed in order to provide surface measurements that may be compared between exposure studies.

USEPA's National Exposure Research Laboratory (Cincinnati) has developed a procedure that uses a cotton gauze pad moistened with 10 mL isopropanol (IPA) wiped across a designated sampling area followed by a second dry wipe in the same direction. The sampling is repeated using a moistened pad (10 mL IPA) followed by a dry wipe in the vertical direction. This method was evaluated using both hard (i.e., ceramic tile) and soft (i.e., carpet) household surfaces contaminated with organophosphate, pyrethroid, and pyrazole pesticides.

Residues were recovered from hard surfaces at mean levels of 94 ? 14% (organophosphates), 98 ? 18% (pyrethroids), and 97 ?21% (pyrazole). Lower recoveries were captured from carpet at 35 ? 7% (organophosphates), 33 ? 5% (pyrethroids), and 35 ? 8% (pyrazole). In comparison, lower recoveries of similar pesticides from carpet have been reported for procedures using smaller IPA volumes and without the 2 dry wipes. Analytical interferences from extracts have also been observed for different gauze pad brands. The method described provides a consistent, reliable surface wipe sampling procedure, without interferences, that can be used in a laboratory or field study.